The present invention relates generally to emergency communications devices and more particularly to ensuring emergency availability of communications devices.
Many new vehicles include systems that provide interactive voice and data services. These systems typically include modems for communicating data, cellular phones for establishing links to call centers, and a backup battery. The backup battery provides an alternative power source if the primary vehicle battery is damaged, disabled, or discharged and if power from the vehicle""s alternator is not available. These systems typically offer a host of available services ranging from informational assistance, such as driving directions, to critical services, such as emergency transmissions in the event of an accident. When no other power source is available, the system provides these various services using power from the backup battery. However, this permits non-critical services, such as routine transmissions of location information, to slowly drain the backup battery when other power sources are unavailable. Thus, in the event of an emergency, the backup battery may be unable to provide sufficient power for emergency communications.
In accordance with the present invention, techniques for ensuring emergency availability of communications devices are provided which substantially eliminate or reduce disadvantages and problems associated with previous techniques. In a particular embodiment, the present invention satisfies a need for a communications device that controls access to various services to ensure that sufficient power remains available in emergency situations.
According to one embodiment of the present invention, an apparatus includes a wireless device, an energy storage device, and a controller. The wireless device provides wireless communications, and the energy storage device provides power for the wireless device and reports an energy level indicating remaining energy for the energy storage device. The controller determines an emergency threshold to provide sufficient power to communicate emergency information using the wireless device, monitors the energy level, and provides wireless services using the wireless device if the energy level exceeds the emergency threshold.
In accordance with another embodiment of the present invention, a method for controlling wireless communications determines an emergency threshold that provides sufficient power for a wireless device to communicate emergency information, monitors an energy level for an energy storage device, and provides wireless services using the wireless device if the energy level exceeds the emergency threshold.
The invention provides a number of technical advantages. When a communications device uses a backup power source to provide power for services, the device can monitor the remaining energy level of the backup power source and provide different levels of service, scaling back services when appropriate to ensure that sufficient power remains for emergency situations. Thus, the device can prevent the backup power source from being completely drained when being used to power routine or non-critical services. For example, if the remaining energy in a backup battery drops below some threshold, a communications device may limit access to all services except emergency communications.
To determine various levels of service, communications devices may use one or more thresholds. For example, a device may use a single emergency threshold that provides sufficient power for emergency communications. When using power from a backup power source, the device provides full services if the power level remaining in the backup source is above the emergency threshold and can restrict these services if the power level drops below the threshold. Thresholds used may be programmable based on determinations of the communications device or based on commands received from remote devices.
In addition, thresholds may be determined based on communications methods available for emergency transmissions. For example, a threshold for a communications device having only satellite communications available may be significantly higher than a communications device having access to a wireless local area network. In addition, a threshold may account for multiple different available communications methods. For example, an emergency threshold may provide sufficient power for attempts at both satellite and cellular emergency transmissions. Furthermore, monitoring the backup energy available allows systems to provide warnings indicating, for example, that a backup battery needs replacing.
In addition to providing different levels of service based on an available energy level, the system may also use the available energy level of a backup battery to select between available power supplies. For example, alternators and primary vehicle batteries typically provide fluctuating and noisy power supplies, while the backup battery may provide a clean and stable power source. Thus, so long as the energy level of the backup battery remains above some operational threshold, the system can provide services using the backup battery as the power source.
Other technical advantages of the present invention will be readily available to one skilled in the art from the following figures, descriptions, and claims.